Extreme pressure lubricant



Patented Dec.- 20, 1938 UNITED STATES 2,141,142 EXTREME PRESSURE LUBRICANT Anderson W. Balaton, Chicago,

Amour and Company, Chicago,

ration of Illinois 111., assignor to 111., a corpohlo Drawing. Application December 21, 1938, Serial No. 117,095

8 Claims.

This invention relates to extreme pressure lu-'- bricants and it comprises, as an extreme pressure lubricant, the reaction product obtained by reacting aliphatic nitriles of relatively high molecular weight with sulphur monochloride, or mixtures of sulphur and sulphur monochloride, it further comprises lubricants composed of such reaction products admixed with mineral lubricants.

In my co-pending application, Serial Number 105,351, filed October 12, 1936, I describe and claim extreme pressure lubricants composed of polymerized aliphatic nitriles. These polymers are made by treating aliphatic nitriles with polymerizing agents such as aluminum chloride under conditions which convert the nitriles to complex oily materials of high molecular weight and unknown constitution. Among the polymerizing agents mentioned in that application are chlorides of sulphur, and, operating conditions are such that the sulphur chloride acts primarily as a polymerizing agent.

In my co-pending application Serial No. 117,094, filed of even date herewith, I have described and claimed as new materials, compounds made by reacting aliphatic nitriles containing at least 10 carbon atoms with sulphur monochloride, or mixtures of sulphur monochloride and sulphur. The operating conditions, particularly temperature, are much less drastic than those employed when the primary reaction of the nitrile is that of polymerization. These new reaction products obtained from such nitriles and sulphur monochloride are dark-colored oils having viscosity characteristics much the same as ordinary lubricating oils of medium grade.

- The present invention is based upon the discovery that these new sulphur monochloride-nitrile reaction products are unusually good lubricants for extreme pressure lubrication, either when used by themselves, or when used in admixture with ordinary mineral lubricants.

Modern high speed machinery has brought about unusual lubricating problems The present tendency in machine design is to use greater unit pressures and higher rubbing speeds. This has resulted in the development of various frictional parts such as hypoid and spiral-bevel gears which cannot be lubricated with ordinary mineral oil lubricants. The pressures and rubbing speeds in these types of gears are so excessive that ordinary mineral oils cannot prevent metal to metal contact and bearing failures result. These failures are due to rupture of the oil films which results in excessive heat at the point of friction. The temperatures encountered under these conditions are so high that the metal parts weld together. In certain types of gear design the maximum stress on the gear-tooth surface may be as high as 350,000 to 400,000 pounds per square inch and the rubbing velocity as high as 1,800 feet per minute.

These lubrication requirements have resulted in the development of so-called "extreme pressure lubricants which contain certain substances which function as anti-weld components. When these treated oils or greases are used in lubrication very high pressures, rubbing speeds and temperatures do not result in failure of the gears through welding because of the presence of this anti-weld component. Various sulfided animal oils have been used generally as the basis-of these lubricants. Recently lead soaps have been used in conjunction with sulflded organic compounds for this purpose.

While the modern type of gearv design demands a lubricant containing maximum load carrying capacity, such factors as stability of the lubricant, low internal friction, of wear are of extreme importance and cannot be disregarded. None of the lubricants now generally used possess all of these properties and usually a lubricant is selected whlchis outstanding in one of these characteristics at the expense of the others. There is a very definite need at the present time for non-corrosive stable lubricants which can function under high unit pressure and rubbing speeds. These lubricants should possess non-corrosion and low rate all of the characteristics generally associated with high grade lubricants, such as low internal friction, oiliness and chemical stability, but in addition must have the ability to prevent metal parts from welding under conditions of high temperature and pressure.

The usefulness of lubricants in extreme pressure lubrication can be tested in various types of machines. Among them is the Faville-LeVally testing device, a machine which has been designed especially for determining the usefulness of lubricating compounds at high bearing pressures. This machine in essence, comprises a steel pin mounted to rotate between two steel blocks having arc-like cavities encircling the pin. The blocks can be moved toward each other by means of jaws, and the actual amount of force used to press the blocks against the pin can be indicated upon a gauge usually running from 0 to about 4,500 pounds. The gauge reading is not inpounds per square inch since the actual area of the blocks in contact with the pin is much less than one square inch. Consequently, the actual pressure per square inch is much greater than that indicated by the gauge. The device also has means to indicate the torque, which is a measure of the resistance to rotation of the pin between the blocks. The actual amount of power required to rotate the pin can be indicated by means of a recording watt meter. The blocks and the pin are immersed in a small container in which the oil to be tested can be placed. A thermometer immersed in the oil is used to record the [temperature of the oil at definite time intervals.

The testing machine is provided with means to tighten up the jaws, and hence press the blocks against the pin in a continuous manner as the test progresses, or the jaw load can be increased intermittently in a period of time. When testing lubricants in such a machine, readings are taken about every five minutes of the temperature, power required to rotate the pin, the actual jaw load, and the torque.

The amount of Wear on the pin can also be determined as the test proceeds.

Before comparing the behaviour of my lubricants under extreme pressure conditions with sulfided fats at present in use, I shall describe methods of making my lubricants.

As stated, my lubricating materials, and by this I mean the products which I use as a lubricant alone or add to a mineral lubricating oil, are all made from aliphatic nitriles containing at least 10 carbon atoms in the molecule. These nitriles are first prepared from the corresponding higher fatty acids such as capric, lauric, myristic, palmitic and stearic. The nitriles can also be prepared from the unsaturated higher fatty acids such as oleic, linoleic and linolenic. All of my nitrile starting materials will have the generic formula RCN, wherein R is an alkyl group having 9 or more carbon atoms. Stearo nitrile can thus be prepared from stearic acid and one of the best ways to prepare this, and all other nitriles embraced within myinvention, is by theaction of ammonia on the corresponding fatty acid. Such processes are described in the Ralston U. S. Patent 2,061,314.

One of the very best sources of fatty acids for conversion to nitriles is the mixture of unsaturated fatty acids obtained from soy bean 011. These fatty acids are oleic, linoleic and linolenic, together with small amounts of saturated fatty acids. In isolatin the fatty acids the soy bean oil can be saponified or hydrolyzed in the usual way.

After preparing the nitriles the next step is the conversion of them to reaction products containing sulphur and chlorine by reacting the nitrile with sulphur monochloride, or mixtures of sulphur and sulphur monochloride.

The nitrile, whether it be a simple nitrile such as stearo nitrile, or nitrile mixtures obtained from mixed fatty acids, is charged into a reaction vessel advantageously provided with a reflux condenser.

To each 10 parts by weight of the nitriles I slowly add one part by weight of sulphur monochloride at room temperature. During the addition of the sulphur monochloride the temperature will rise to about 50 or 60 C. The mixture is then allowed to stand, usually about 12 hours and finally heated for about 6 hours at a temperature of about 50 to 60 C. I avoid the use of high temperatures, above the boiling point of the sulphur monochloride, namely 135 C., because such high temperatures lead to the formation of heavy polymers which are not as satisfactory for extreme pressure lubrication. The reaction product, which requires no further purification or treatment, is a dark-colored oily material very much like a lubricating oil, but it has no noticeable odor of chlorine or sulphur monochloride. The chlorine and sulphur appear to be firmly bound to the nitrile molecule. The product is non-corrosive towards metals which is, of course, very important in the lubrication arts.

The amount of sulphur monochloride to be added to the nitrile is generally about one-tenth the quantity of nitrile. An excess does no harm since it can be removed readily by distillation under a moderate vacuum.

As indicated above, I can use mixtures of free sulphur and sulphur monochloride and obtain about the same product. Thus, for example, I add about 20 parts by weight of flowers of sulphur to about 200 parts by weight of crude soy bean fatty acid nitriles and then slowly add about 20 parts by weight of sulphur monochloride. In this modification it is advantageous to heat the reaction mixture at a temperature of about 60 C. for about 6 hours and finally increase the temperature to about C. for about 30 minutes. During the reaction most of the sulphur goes into solution and reacts with the nitrile. Any unreacted residual sulphur can be filtered off readily. The actual composition of the final product which is also an oily material is not known.

In broad aspects then, the present invention is based upon the discovery that sulphur monochloride-aliphatic nitrile reaction products have the useful property of functioning as extreme pressure lubricants, either alone or in admixture with mineral lubricating oils such as a Pennsylvania bright stock. I shall now compare the behaviour of my materials with common lubricants advocated for extreme pressure purposes. In the following table the nitrile mentioned is that made from soy bean fatty acids, the material itself being the reaction product of sulphur monochloride with such nitrile.

The lead soap base mentioned above is one of the usual mixtures of lead soaps and mineral lubricants, and the sulfided lard oil base is a common mixture of a mineral lubricant with sulfided lard. In the above table the loading on the jaw which presses the blocks against the pin iscontinuous. It is to be noted that the nitrile alone carried a higher load than either the lead soap base or the sulflded lard oil base, and the mixture of 25% reaction product of sulphur monochloride and nitrlle with 75% of Pennsylvania bright stock carried a load which is entirely satisfactory. It should also be noted that the temperature rise with the treated nitriles is less than the comparison oils. Likewise, power requirements to rotate the pin immersed in the mixture of treated nitriles and bright stock are less than the comparison oils.

Table 2 which follows, shows the behaviour of soy bean fatty acid nitriles treated with sulphur monochloride and sulphur.

A marked improvement in load carrying capacity over the lead soap base and sulfided lard oil base is evident In both Tables land 2 the load on the jaws, which forces the blocks against the rotating pin is continuous. This indicates the ability of the lubricant in question to withstand shock loads. When loading is intermittent, in other words,

the load is increased pounds every five minutes, the tests indicate the ability of the lubricant to withstand high temperature rise and high torque conditions. The wear on the pin can also be determined.

Table 3, which follows, indicates the results observed when a commercial lubricant such as a sulfided lard 011 base is used. By reference to the table it will be noted that as-the load increases by 100 pound increments the temperature rises rapidly, the torque increases and the power required to rotate the pin increases. After 74 minutes elapsed the lubricant fails to function and the temperature rise at this time is 311 F. The lubricant tested in Table 3 is one commonly recommended for the lubrication of hypoid gears.

Table 3 Tem- Load Torque pera- Power Time, minutes carried, in ture kilopounds pounds lsie, watts 100 3 17 0. 04 200 20 52 i9 300 26 96 225 400 24 122 225. 500 59 190 58 600 55 237 52 700 50 25B 47 800 53 279 48 900 48 287 v .42 1,000 48 292 385 1, 100 50 295 39 1,200 50 304 43 1,300 51 311 43 Failed shows the results obof 75% Pennsylvania sulphur monochloride- Table 4 which follows tained when a. mixture bright stock and 25% treated nitriles is used. The nitriles are those made from soy bean fatty acid nitriles and sulphur chloride as described above.

Table 4 Load Torque Tempera- Time, minutes carried, in ture rise, E-saga pounds pounds F. 2

100 4 17 0.045 200 5. 5 30 055 300 7 40 075 400 8 52 .095 500 10 04 600 11 77 700 13 88 800 14 08 900 14 105 145 1,000 14 109 145 1, 100 14 114 l5 1, 200 14. 5 118 16 1,300 15 124 l, 400 16 132 l, 500 17 140 205 1, 600 17 146 225 l, 700 17 153 V .235 1, 800 17 162 26 l, 900 18 175 305 2,000 30 199 .405

It is to be noted especially that the lubricant of Table 4 functions perfectly after a period of 115 minutes when the jaw load has reached 2,000 pounds. The torque is nearly half that noted in connection with the ordinary lubricant of Table 3 and the temperature rise after 105 minutes is only 199 in comparison with a rise of 311 after '74 minutes in Table 3. Likewise, the power requirements are very much less, for example, at the end of 75 minutes in Table 4 the power required to rotate the pin is only 0.185 in comparison with a power requirement of 0.43 in Table 3.

These products are also tested in a specially constructed machine which operates under 90,000 pounds pressure per square inch with a rubbing speed of 2,600 feet per minute. This machine is extremely diflicult to lubricate and commercial lubricants have failed to prevent welding of the metal parts. My nitrile-sulphursulphur monochloride products lubricated this machine under full load conditions for 5 minutes without wear and without apparent development of metal to metal contact.

From the above data it is apparent that the lubricants of the present invention are much more satisfactory for extreme pressure lubrication than the common lubricants at present advocated for such purposes. My lubricants withstand higher bearing pressures and show a much lower temperature rise and power requirement than ordinary lubricants. The wear on the pin is also less when the lubricants of the present invention' are used. In addition, my lubricants are not corrosive, and they are heat-stable under all conditions encountered in gear lubrication.

In the interest of brevity I have given data for products obtained from soy bean fatty acid nitrlles and sulphur monochloride. Similar results are observed when other nitriles are used as initial starting materials, and I do not wish to be, limited to any specific nitrile. Improvement in extreme pressure lubrication is general when I use products made from all aliphatic nitriles containing 10 or more carbon atoms which have been treated with sulphur monochloride or mixtures of sulphur and sulphur monochoride as described above.

It will, of course, be understood that my sulphur monochlorlde-treated nitriles can be admixed with any of the ordinary petroleum lubricating oils in any desired proportion. In the preceding description I have confined specific examples of lubricant mixtures to Pennsylvania bright stock and the treated nitrile. Other lubricating oils and greases can, of course, be used instead of the Pennsylvania bright stock and my invention is not limited to the use of any particular petroleum hydrocarbon base.

Having thus described my invention, what I claim is:

1. An extreme pressure lubricant comprising a relatively large amount of a mineral lubricating oil and a smaller amount ofthe reaction product obtained by reacting sulphur monochloride with an aliphatic nitrile having the formula RCN wherein R is an alkyl radical having at least 9 carbon atoms, at a temperature not in excess of C.

2. An extreme pressure lubricant comprising a relatively large amount of a mineral lubricating oil and a smaller amount of the reaction product obtained by reacting sulphur monochloride with an aliphatic nitrile having the formula RCN wherein R is an alkyl radical having 17 carbon atoms, at a temperature not in excess of 135 C.

3. An extreme pressure lubricant comprising a relatively large amount of a mineral lubricating oil and a smaller amount of the reaction product obtained by reacting sulphur monochloride with an unsaturated aliphatic nitrile having the formula RCN wherein R is an unsaturated alkyl radical having 17 carbon atoms at a temperature not in excess of 135 C.

4. An extreme pressure lubricant comprising a relatively large amount of a mineral lubricating oil and a smaller amount of the reaction product obtained by reacting sulphur mono-' 1 ride and sulphur with an aliphatic nitrile having the formula RCN wherein R'is an alkyl radical having at least 9 carbon atoms, at a tempera ture not in excess of 135 C.

6. An extreme pressure lubricant comprising a relatively large amount of a mineral lubricating oil and a smaller amount of the reaction product obtained by reacting sulphur monochloride and sulphur with an aliphatic nitrile having the formula RCN wherein R is an alkyl radical having 1'7 carbon atoms, at a temperature not in excess of 135 C.

7. An extreme pressure lubricant comprising a relatively large amount of a mineral lubricating oil and a smaller amount of the reaction product obtained by reacting sulphur monochloride and sulphur with an unsaturated aliphatic nitrile having the formula RCN wherein R is an unsaturated alkyl radical having 17 carbon atoms, at a temperature not in excess of 135 C.

8. An extreme pressure lubricant comprising a relatively large amount of a mineral lubricating oil and a smaller amount of the reaction product obtained by reacting sulphur monochloride and sulphur with soy bean fatty acid nitriles, at a temperature not in excess of 135 C.

ANDERSON W. RALSTON; 

